Chronic obstructive pulmonary disease (COPD) is a serious progressive lung disease which makes it harder to breath. It currently affects over fifteen million people in the United States alone and is currently a leading cause of death in the country. The overwhelming primary cause of COPD is inhalation of cigarette smoke, responsible for over 90% of COPD cases. The economic and social burden of the disease is both substantial and increasing.
FIG. 1 depicts a healthy set of lungs 10 in an individual. A windpipe or trachea 12 connects the nose (not shown) and mouth (not shown) to the lungs 10. As air flows in through the nose and mouth of an individual, the trachea 12 transports the air to the lungs 10 for respiratory functions. The trachea 12 divides into the left 14 and right 16 bronchus stems, which further divide into a plurality of bronchi 18, bronchioles 20, and eventually, terminate in a plurality of alveoli 22. The alveoli 22 are small air sacs which enable gas exchange with the individual's blood stream. That is, they permit oxygen diffusion into the blood stream, and receive and expel CO2 during exhalation.
COPD includes emphysema. As shown in FIG. 2A, emphysema may be characterized by the destruction of lung parenchyma 24, the functioning parts of the lungs 10. The parenchyma 24 includes the alveoli 22 walls, bronchioles 20, and the bronchi 18. Destruction of these tissues results in progressively increasing shortness of breath called dyspnea. As it worsens, emphysema turns the healthy alveoli 22, clustered like bunches of grapes, into large, irregular pockets with gaping holes in their inner walls, as shown in FIG. 2B. This reduces the surface area of the lungs and, in turn, the amount of oxygen that reaches an individual's blood stream.
Emphysema also slowly destroys the elastic fibers or tethers that hold open the airways, including the bronchioles 20 and bronchi 18, leading to the alveoli 22. This destruction may cause airways to reduce in diameter or collapse when one breaths out, which prevents the air in your lungs, including CO2, from escaping during exhalation. A significantly reduced diameter airway 26 is depicted in FIG. 2B. A failure to exhale may result in hypercapnia, high blood gas levels of CO2. Hypercapnia can lead to acidosis (lowering of pH levels), which is correlated to a significantly greater risk of mortality in COPD patients.
Treatment may slow progression of emphysema, but it cannot reverse any damage already sustained. In some cases, surgery may be required for treatment of emphysema. Surgery may include lung volume reduction (LVR) surgery, which removes or otherwise decreases damaged tissue in order to assist remaining, healthy tissue to function more efficiently. In severe cases, lung transplant surgery may be necessary.